What it does
Closing the fourth wall
An enclosure blocks light on three sides. The back cover is the fourth.
Light in, light out
Carl’s describes the job plainly: keep ambient light from leaking in and projector light from leaking out. The picture reads as a picture, not a bright rectangle in a lit room.
Sized to the enclosure
Six sizes, one per Pro opening. The option here is the enclosure size, in Carl’s own tokens, so a 9 × 12 cover goes on a 9 × 12 enclosure and nothing else.
The pipe decision
Carl’s sells the cover and its pipes separately and says why: if you are cutting your own conduit for the enclosure, you may want to cut the cover’s too. The pre-cut kit is here for the buyer who would rather not.